The present invention relates to electronics module connectors having a novel mechanical electrostatic discharge (ESD) protector.
It is now well known in many forms of electronics equipment to package circuitry in an modular assembly known as a Line Replaceable Module (LRM). It is highly desirable to prevent electrostatic discharge (ESD) damage to electronics equipment in such modules. It is relatively easy to prevent ESD damage when the LRM is installed in equipment racks housing a grounded chassis, as by providing the LRM with a conductive case which is connected to the conductive ground circuitry of the rack in which the case is installed; however, it is much more difficult to protect against ESD damage during "field" handling, when the LRM is "free-floating" and is not connected for normal discharge, i.e. surrounding air and/or package materials prevent conduction through to ground potential. One portion of an LRM particularly susceptible to ESD and the like damage is the multi-contact input/output connector typically found on the rear panel of the module; this connector has conductive pins connected to active circuitry within the module. One solution to damage by high voltages, caused by electrostatic discharge or the like, at these LRM input connector pins has been to protect the internal circuitry attached to the individual pins; the form of protection usually comprises an array of diodes and/or resistors which act by clamping action to limit the high voltage ESD reaching the LRM interior active circuits to a lower, safe volt level. These clamping electronic circuits generally have several disadvantages, which include: some module volume, already generally in short supply, must be utilized for the protective clamping circuitry; if the clamping circuitry requires an active voltage to which the higher voltage must be clamped, then that higher voltage may not be present when the module is removed from the rack and is disconnected from a potential source; self test of the protective circuitry is very difficult to achieve, so that functionality may be problematic at best; and active circuit throughput and other performance characteristics may be degraded by the addition of extraneous elements at the LRM input/output connection pins. It is therefore highly desirable to provide a protective device which can be combined with existing modules and their conductive cases and/or module connector shells, to provide a mechanical protective device which increases ESD protection to the module whenever that module has been removed from the rack or apparatus into which it is to be installed, and whenever the module is in a normally ungrounded condition, as during transit and the like.